The present invention relates to a developing process for reproduction layers using an aqueous electrolyte developer.
Light-sensitive reproduction layers are used, for example, in the preparation of offset printing plates or in the preparation of photoresists (both referred to hereinafter as copying materials). In general, such layers are applied to a support by the customer or industrial manufacturer. The supports used for such copying materials include metals such as zinc, magnesium, chromium, copper, brass, steel, silicon, aluminum or combinations of these metals, plastic films, paper or similar materials. These supports can be coated with the light-sensitive reproduction layer without a surface modifying pretreatment of the support, but preferably the coating step is preceded by surface modification such as mechanical, chemical and/or electrochemical roughening, surface oxidation and/or treatment with agents which impart hydrophilicity (for example in the case of supports for offset printing plates). In addition to at least one light-sensitive compound, conventional reproduction layers usually also contain an organic binder (resins or the like) and, optionally, also plasticizers, pigments, dyestuffs, wetting agents, sensitizers, adhesion promoters, indicators and other customary additives. In order to produce an image from the reproduction layers, the layers are developed after their exposure to obtain a printing plate, a photoresist, or similar article.
A developer for negative-working reproduction layers must be able to dissolve out of the exposed layer those parts of the layer (the non-image areas) which have not been struck by electromagnetic radiation (for example light), without significantly affecting those parts (the image areas) of the layer which have been struck by the radiation. U.S. Pat. No. 3,867,147 lists as examples of suitable developers: water, water/organic solvent mixtures, aqueous salt solutions, aqueous acid solutions, aqueous alkaline solutions and undiluted organic solvents to which, if appropriate, surfactants and/or agents imparting hydrophilicity can be added. The developers chiefly used in the examples of the aforementioned patent contain water, sodium lauryl-sulfate, sodium sulfate, tartaric acid and, optionally, benzyl alcohol. Other developers contain isopropanol, n-propanol, n-propyl acetate, polyacrylic acid, 1,1,1-trichloroethane, acetone or ethylene glycol monomethyl ether.
A developer for positive-working reproduction layers must be able to dissolve out of the exposed layer those parts of the layer (the non-image areas) which have been struck by electromagnetic radiation, without significantly affecting those parts of the layer (the image areas) which have not been struck by the radiation. U.S. Pat. No. 3,110,596 lists as examples of suitable developers alkaline aqueous solutions of phosphates, silicates, fluorosilicates, stannates, fluoroborates or fluorotitanates, which optionally may also contain water-soluble hydrocolloids or organic solvents.
A "developer" or "decoating agent" for electrophotographic reproduction layers must be able to dissolve out of the layer the non-image areas remaining after (a) charging of the reproduction layer containing a photoconductor, (b) exposure of the charged layer and (c) application of toner and fixing of the resulting latent electrostatic image, without significantly affecting the image areas of the layer. German Pat. No. 1,117,391 lists as examples of liquids suitable for this purpose: inorganic or organic bases in aqueous solutions to which organic solvents can also be added. Specific examples include octylamine in polyethylene glycol, morpholine, sodium silicate and carboxymethylcellulose in water monoethanolamine, diethanolamine, methanol, ethylene glycol, glycerol and sodium silicate; aqueous NaOH solution; and aqueous NH.sub.3 solution with polyethylene glycol.
The developing processes known in the prior art for exposed reproduction layers work on the principle of a differentiation in solubility between exposed and non-exposed areas and parts of the layer. The pH values of suitable developers therefore frequently differ from neutral, and they contain more or less large amounts of organic solvents. The content of active ingredients in known developers, in addition to water as the desired standard solvent, are in general above about 5 to 10 percent by weight, so that the developers represent an increasingly undesirable effluent burden. Moreover, in practice, developers having a specific action are marketed for most of the wide variety of reproduction layers available and such developers are not suitable for developing other reproduction layers. Typical developing times in the known processes are between 15 and 120 seconds.